28 Dec
2003
28 Dec
'03
1:40 p.m.
On Sun, 28 Dec 2003 17:31:39 -0500, Chad Fernandez
<fernande(a)internet1.net> wrote:
[snip...]
Just got back from Radio Shack. I bought a fast
blowing 250v 2 amp
fuse
and installed on in the laserdisc player. Unfortunetly, it blows just
as fast as the .75amp fuse.
[hack...]
There is a chance that after sitting all that time the filter cap has
become unpolarized. Every time you turn the thing on the current surge
required to charge the cap will blow a fast blow.
What you might try is to get a variac, turn it down all the way, attach
the laserdisk, turn it on and then slowly bring the variac to the full
voltage. This will give the cap a chance to repolarize without pulling
too much current. If the fuse still blows you probably blew the input
rectifier or something else expensive...
CRC
29 Dec
29 Dec
9:11 a.m.
What you might try is to get a variac, turn it down
all the way, attach
the laserdisk, turn it on and then slowly bring the variac to the full
voltage. This will give the cap a chance to repolarize without pulling
Be _very_ careful if you try this. A switch-mode PSU (which this almost
certainly is) acts as an almost perfect constant power load. That is to
say, the lower the input voltage, the more current it tries to draw. Some
SMPSUs will blow up spectacularly on a low input voltage.
If you want to re-form the filter capacitor (and to be honest, I'd just
replace it if it was shorted), remove it from the PSU, or at least
disconnect the chopper circuit, etc.
-tony
7663
days inactive
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